1. Field of the Invention
The present invention relates to a fieldbus adapter that is connected between a fieldbus that handles a digital signal and a field device that handles an analog signal.
Priority is claimed on Japanese Patent Application No. 2011-165408, filed Jul. 28, 2011, the content of which is incorporated herein by reference.
2. Description of the Related Art
All patents, patent applications, patent publications, scientific articles, and the like, which will hereinafter be cited or identified in the present application, will hereby be incorporated by reference in their entirety in order to describe more fully the state of the art to which the present invention pertains.
Currently, protocols used for a fieldbus include HART, FOUNDATION fieldbus, PROFIBUS, BRAIN, ISA100.11a, etc. HART, BRAIN and the like realize digital input/output while using resources of an analog control system by overlapping a digital signal with an existing analog current output of 4 to 20 mA. In addition, in FOUNDATION fieldbus and ISA100.11a, measurement and calculation functions of devices are connected by using a function block to build an autonomous control system.
When introduction of the autonomous control system of a FOUNDATION fieldbus, ISA100.11a or the like is attempted while using resources of an analog control system, the existing fieldbus of HART, BRAIN or the like is not available since there is no compatibility with the existing fieldbus of HART, BRAIN or the like. Accordingly, resources of the analog control system cannot be incorporated into the autonomous control system.